As the main drive motor for vehicle mounted on a bogie frame (bogie) under a floor of a railway vehicle, an open type main motor (in an open type self-ventilation cooling system) has been adopted conventionally. In the open type main motor, its rotor shaft is provided with a fan rotatable with the rotor shaft. With the rotation of the fan, outside air is sucked into the main motor. Then, the outside air circulates in the main motor and cools down a rotor and a stator.
In this open type self-ventilation cooling system, a ventilation strainer is arranged at an intake part (intake port) of the system in order to prevent an interior of the motor from being damaged by dust mixed in so-sucked cooling air (inflowing outside air). This ventilation strainer traps the dust in the inflowing outside air by means of a filter in the strainer.
In order to prevent an excessive rising of temperature of the motor, which is caused by an increase in the inflowing outside air due to the filter's clogging, it is necessary to clean up the filter at relatively-short intervals.
However, with a difficulty that the filter can trap dust perfectly, the dust entering into the motor adheres to its inside for gradual deposition to cause motor's insulating performance and cooling effect to deteriorate. Therefore, it is necessary to disassemble the motor periodically and clean up it to remove the inside dust.
On the contrary, in order to meet the request of labor-saving in maintenance and the request for low-noise operation, there is developed a totally enclosed type main drive motor including an interior fan. This totally enclosed type main drive motor for vehicle is adapted so as to prevent the dust in addition to the outside air from entering the interior since it is shut off from the outside. Thus, the same main drive motor is adapted so as to prevent inside windings from being damaged by the dust, thereby suppressing an increase in the frequency of maintenance and inspection due to this damage.
Additionally, since this totally enclosed structure can prevent a dispersion of noise generated due to the interior fan's rotating, it is also possible to provide an eco-friendly motor.
Meanwhile, a main drive motor for vehicle is required to have a large capacity with the speeding-up for a train. However, due to a situation where the mounting position belongs to a limited narrow space in a bogie frame mentioned later and also the above speeding-up for a train, both miniaturization and weight saving are required for the main drive motor for vehicle.
In order to deal with these conflicting requests, it is contemplated to improve the heating resistance of insulating resin for windings. From the viewpoint of preventing deterioration of the insulating resin and maintaining the insulating characteristic for long-period operation, nevertheless, it is necessary to improve the cooling performance of a main motor for driving a vehicle.
For instance, Japanese Patent Laid-Open Publication No. 9-205758 discloses a type of totally enclosed type main drive motor intended to improve this cooling performance. FIG. 1 is an axial sectional view of an upper part of this totally enclosed type main drive motor for a vehicle. FIG. 3 is a sectional view taken along a line III-III of FIG. 1. FIG. 4 is a plan view of a condition that the totally enclosed type main drive motor for vehicle is mounted on a vehicle bogie. FIG. 5 is a sectional view taken along a line V-V of FIG. 4.
In FIG. 2 to FIG. 4, a vehicle body 101 shown with a chain double-dashed line is mounted on a bogie frame 102 H-shaped in plan view. The totally enclosed type main drive motor for vehicle is built in between an attachment seat 104 on an inner frame 102 of the bogie frame 102 and an axle 105.
The motor includes an outer casing frame 1 in the form of a bottomed cylinder made from mild steel plates and is attached to the vehicle so that a central axis of the outer casing frame 1 is horizontal and perpendicular to the traveling direction of the vehicle. On an upper part of the peripheral wall of the outer casing frame 1, an upper attachment seat 2 is formed so as to project to rearward in the vehicle traveling direction. On the lower part of the peripheral wall of the outer casing frame 1, a lower attachment seat 3 is formed so as to project to rearward in the vehicle traveling direction. On the upper part of the peripheral wall of the outer casing frame 1, additionally, a pair of hooks 4A, 4B are formed so as to project to forward in the vehicle traveling direction.
As shown in FIGS. 2 and 4, the upper attachment seat 2 is mounted on the top end of the attachment seat 104 through a key 106 and further fixed to the attachment seat by bolts 5. The lower attachment seat 3 is fixed to a lower beam 107 of the bogie frame 102 by bolts 5 while making contact with the front surface of the lower beam. Again, the upper attachment seat 2 and the lower attachment seat 3 are respectively formed with hook holes 6 for suspension.
In the totally enclosed type main drive motor for vehicle, as shown in FIG. 4, a small spur gear 9 is connected to a leading end of a rotor shaft 7 through a flexible joint 8. A large spur gear 10 fixed to an axle 105 meshes with this small spur gear 9. Note that the small spur gear 9 and the large spur gear 10 are accommodated in a gear box 11.
As shown in FIG. 1, an annular bracket 13 is mounted on an opening surface of the outer casing frame 1. On the circumferential part of the bracket 13, a fitting part 14 is formed so as to project to the inside of the outer casing frame 1. This fitting part 14 is inserted into the inside of the outer casing frame 1 and fixed to the outer casing frame 1 by a plurality of bolts (not shown).
A roller bearing 15 is inserted into a bearing hole formed at a center part of the bracket 13 and fixed to it. The roller bearing 15 has its outer ring fixed to an external side of the center part of the bracket 13 by a plurality of bolts 16 (see FIG. 3). Throughout both inside of the motor and the outside, the rotor shaft 7 is inserted into an inner ring of the roller bearing 15 and fixed to it.
From the inside of the outer casing frame 1, a housing 17 is inserted into a through-hole formed at the center of an end wall on the opposite side of the opening end of the outer casing frame 1 and fixed to the outer casing frame 1 by a plurality of bolts (not shown) from the inside of the frame.
A ball bearing 18 is inserted into a bearing hole formed at the center of the housing 17. The ball bearing 18 has its outer ring fixed to the housing by a bearing presser 19. This bearing presser 19 has a fitting part inserted into the bearing hole from the outside of the housing 17 and is fixed to the housing 17 from the outside, by bolts (not shown).
The rotor shaft 7 is fitted into the roller bearing 15 and the ball bearing 18 under pressure, in advance. A rotor core 20 is fitted to a substantially-intermediate part of the rotor shaft 7 in the longitudinal direction under pressure. On one end of the rotor core 20, a core presser 21 annularly formed by a thick plate is fitted to the rotor shaft 7 under pressure. On the other end of the rotor core 20, a core presser 22 is fitted to the rotor shaft 7 under pressure. Between the core presser 21 and the bracket 13, a fan 23 is fitted to the rotor shaft 23 under pressure.
As shown in FIG. 1, the rotor core 20 has a plurality of ventilation holes 24 formed around a central axis of the rotor core 20 so as to extend in the axial direction. Rotor bars 25 are inserted into an outer circumferential part of the rotor core 20 and fixed to it. End rings 26 are brazed to respective both ends of the rotor bar 25.
While, a stator core 27 is press-fitted to an inner circumference of the outer casing frame 1, at its intermediate part. Arranged on the inner circumferential side of the stator core 27 is a stator coil 28 that is inserted into slots (not shown) and includes both ends projecting from the stator core 27. With this structure, this main motor constitutes a squirrel-cage induction motor.
The outer casing frame 1 has oblong ventilation openings 29A, 29B formed at both axial ends of an upper part of the peripheral wall of the outer casing frame 1. These ventilation openings 29A, 29B are positioned on the side of the axle 105, in the upper part of the outer casing frame 1. Connective parts 30A, 30B in the form of crowned tubes with opened bottoms are welded to an outer surface of the peripheral wall of the outer casing frame 1 and also communicated with the ventilation openings 29A, 29B, respectively.
A plurality of ventilation tubes (pipes) 31 made from steel plates are welded to opposing inside surfaces of the connective parts 30A, 30B in a state that respective ends of the tubes 31 penetrate the parts 30A, 30B. These ventilation tubes 31 are made from thin mild steel plates and penetrate a plurality of cooling fins 32 standing on the outer casing frame 1 at even intervals. The cooling fins 32 are respectively welded to the ventilation tubes 31 and have respective lower ends welded to the upper surface of the outer casing frame 1. A cooler 33 is formed by the connective parts 30, the ventilation tubes 31 and the cooling fins 32.
In the so-constructed totally enclosed type main drive motor for vehicle, at a train's traveling, the fan 23 is also rotated with the rotation of the rotor shaft 7, so that “in-motor” air blown out of the fan 23 enters into the connective part 30A through the ventilation opening 29A illustrated on the left side of FIG. 1, subsequently flows through the ventilation tubes 31 and finally enters into the other connective part 30B on the right side.
Then, this air enters from the connective part 30B on the right side into the interior of the outer casing frame 1 via the ventilation opening 29B and is sucked into the fan 23 through the intermediary of a gap defined between the inner circumference of the stator core 27 and the outer circumference of the rotor core 20.
Additionally, the air entering into the right interior of the outer casing frame 1 partially flows toward the fan 23 through the ventilation holes 24 formed in the rotor core 20 and is sucked into the fan 23 similarly. Thereafter, the air flows in the above way.
In the so-constructed totally enclosed type main drive motor for vehicle, as the stator core 27, the stator coil 28, the rotor core 20 and the rotor bars 25 are cooled down by the air flowing in the motor, the stator coil 28 and the rotor bars 25 both insulated from the stator core 27 by resin, such as epoxy, are capable of maintaining their insulation characteristics of insulating resin to the stator core 27 and the rotor core 20 for the long term. Additionally, since the motor does not take in cooling air from the outside, it is possible to prevent both adhesion and deposition of dust and also possible to prevent an increase in the frequency of maintenance and inspection.
Meanwhile, when incorporating the so-constructed totally enclosed type main drive motor into a bogie, it is performed to gradually lower the motor from the upside of the bogie before mounting the vehicle body thereon. Then, the upper attachment seat 2 on the left side of FIG. 5 is mounted on the top end of the attachment seat 104 of the bogie frame 102 through the key 106 and successively, the upper attachment seat 2 and the lower attachment seat 3 are fixed to the attachment seat 104 and the lower beam 107 by the bolts 5, respectively.
Further, in case of checking on the totally enclosed type main drive motor for vehicle periodically, the bolts 5 are unfastened after detaching the bogie frame 102 from the vehicle body 101 and successively, the motor is lifted up through the use of the hook holes 6.
Note that this totally enclosed type main drive motor for vehicle in the assembled condition shown in FIG. 5 is positioned between the left attachment seat 104 and a right case for the axle 105. Additionally, as shown in FIG. 4, the motor is accommodated between bilateral wheels 108A, 108B in the axial direction, together with the flexible joint 8 and the gear box 11. As shown in FIG. 5, the motor is opposed, on the upper side, to the lower end surface of the vehicle body 101 and also opposed, on the lower side, to a rail 109 at an interval of a height limit H between a set-up leg 29 of the outer casing frame 1 and the top surface of the rail 109. Thus, the motor is assembled in a limited space with no room.
Regarding the so-constructed totally enclosed type main drive motor for vehicle, for not only the above-mentioned miniaturization and large capacity but price-reduction of the vehicle and labor-saving in maintenance/inspection, it is also required to reduce the number of motors composing a train. For that purpose, the motor is required to have a larger capacity.
To this end, there may be contemplated a method of supply the interior of the outer casing frame 1 with large volume of cooling air via a duct by an air blower in a different position. However, this method causes the price of a vehicle to be increased due to the arrangement of the duct. Additionally, as the frequency of maintenance/inspection is increased due to the exchange of a filter in a ventilation strainer and the noise radiated to the outside is also increased, the method cannot agree to the request of the times.
To this end, it may be also contemplated to increase an area of each cooling fin 30 shown in FIG. 3. However, as previously mentioned with reference to FIGS. 4 and 5, this totally enclosed type main drive motor for vehicle is accommodated between the attachment seat 104 and the right case for the axle 105 and arranged in the limited narrow space due to the above arrangement where the motor is opposed, on the upper side, to the lower end surface of the vehicle body 101 and also opposed, on the lower side, to the rail 109 through the height limit H. Accordingly, it is impossible to adopt this countermeasure, similarly.
FIG. 6 is a graph showing velocities of the traveling winds passing through the main motor under a vehicle floor with a vehicle's traveling. In the figure, a line A designates a velocity of wind flowing through the upper part of the main motor, a line B a velocity of wind flowing on the lateral surface of the central part of the traction moor and a line C designates a velocity of wind flowing through the lower part of the main motor. From this graph, it will be understood that the wind velocities of the lower part and the central part of the main motor are larger than the wind velocity of the lateral surface of the central part.
The requests of enhanced power-output and prolonged insulation-life against the totally enclosed type main drive motor driven under such a condition, which could be brought by improving its cooling efficiency, are increasingly apt to grow larger from now on, in the light of coping with the speeding up of vehicles and also laborsaving the maintenance/inspection for vehicles. Additionally, it should be noted that the conventional motor involves the following problems.
First, since the cooler has ventilation passages 14a formed by a number of gathered pipes and compartmentalized by a number of radiator fins 32, dust and paper/rag in the outside air are easy to adhere to the cooler, so that the cooling performance deteriorates since such impurities clog gaps among the pipes with the passage of usage period. Therefore, it is necessary to remove dust and rag from the cooler by blowing air (compressed air) against the cooler periodically. Nevertheless, due to the complexity of the pipes 31 intersecting with the radiator fins 32, it is difficult to eliminate the dust etc. adhering to deep portions of the cooler.
Secondly, since the ventilation route from the ventilation opening 29A to the pipes 31 has a ventilation area sharply narrowed by wall parts among the pipes 31, the ventilation resistance of loss at respective inlets for the pipes increases. FIG. 2 is representative of the flowing of winds in the totally enclosed type main drive motor for vehicle of FIG. 1 by means of arrows. From the figure, it is found that back-tracking vortexes are produced at the inlets of the pipes 31.
Therefore, the circulation movement in the cooler and the motor as a whole deteriorates to cause a reduction in the cooling efficiency of the whole motor.
In a totally enclosed type main drive motor having the conventional piping structure, it is unavoidable that the motor is large-sized because of its inferior cooling efficiency, in comparison with an opened self-ventilation cooler type main drive motor.
Thirdly, due to the structure where the circumferences of the pipes 31 are joined to the radiator fins 32 by welding, an operator has to perform just as many welding operations for the pipes and the radiation fins as there are, causing an inferior commercial production and a rise in manufacturing cost.
Therefore, an object of the present invention is to provide a totally enclosed type main drive motor for vehicle, which can improve the cooling effect and reduce both size and weight of the motor and that allows a laborsaving of maintenance, a reduction in manufacturing cost and a prolongation of the motor's operational life.